Event Emitter

A modern, lightweight Event Emitter for JavaScript and TypeScript, inspired by the Observer Pattern.

Key features:

• 🚀 Simple API: add, emit, remove, addOnce, removeAll
• 🧑‍💻 TypeScript-first: Full type safety out of the box
• ✨ Both callback and Promise/async usage: await emitter.addOnce()
• 🦺 Memory-safe: Listeners can auto-remove with AbortController
• ⚡ Zero dependencies, production-ready, tiny footprint

Use it for events, hooks, signals, or decoupled reactive design!

Installation

npm install tahasoft-event-emitter

Usage

import { EventEmitter } from 'tahasoft-event-emitter';

Basic Example

/** @type {EventEmitter<string>} */
const onStatusChange = new EventEmitter();

onStatusChange.add(status => {
	console.log('Status changed to:', status);
});

onStatusChange.emit('Ready');

Usage in a Class

class User {
	constructor() {
		/** @type {EventEmitter<string>} */
		this.onStatusChange = new EventEmitter();
	}

	updateStatus(status) {
		this.onStatusChange.emit(status);
	}
}

const user = new User();
user.onStatusChange.add(status => {
	console.log('New status:', status);
});

user.updateStatus('Active');

TypeScript Example

class User {
	public onLogin = new EventEmitter<string>();

	public login(userName: string, password: string) {
		// validate...
		this.onLogin.emit(userName);
	}
}

const user = new User();

user.onLogin.add(name => {
	console.log(`User ${name} has logged in`);
});

user.login('John', '1234abcd');

Advanced Usage

One-Time Listeners

Execute a listener only once, then remove automatically:

onStatusChange.addOnce(status => {
	console.log('This runs once for status:', status);
});

onStatusChange.emit('Online'); // Triggers above
onStatusChange.emit('Offline'); // Listener is not called again

Promise/Async-Await Style

Wait for the next event occurrence with a promise:

async function waitForStatus() {
	const newStatus = await onStatusChange.addOnce();
	console.log('Status awaited:', newStatus);
}
waitForStatus();
onStatusChange.emit('Loaded');

Cleanup with AbortController

Auto-remove listeners using AbortSignal:

const controller = new AbortController();
onStatusChange.add(status => console.log('Listen once, then remove automatically if aborted:', status), {
	signal: controller.signal
});

// Later...
controller.abort(); // Listener is removed

API Reference

Add Listeners

add(listener, options?)
addListener(listener, options?)
addEventListener(listener, options?)
subscribe(listener, options?)

options can include { signal: AbortSignal } for automatic removal.

Remove Listeners

remove(listener);
removeListener(listener);
removeEventListener(listener);
unsubscribe(listener);

Remove All Listeners

removeAll();
removeAllListeners();

Emit an Event

emit(arg);
dispatch(arg);

The arg is passed to all listeners.

One-Time Listeners

• Callback form:
  addOnce(listener, options?)
• Promise form:
  await addOnce(options?) resolves with the next value emitted.

Listener Options

{ signal: AbortSignal } – pass an AbortController signal for automatic listener removal:

const controller = new AbortController();
emitter.add(listener, { signal: controller.signal });
controller.abort(); // listener removed

Why Choose This EventEmitter?

• Strictly typed for single-argument events—works great with primitives or objects.
• Promise/async support for modern codebases.
• Abortsafe: no memory leaks—auto-cleanup with AbortController.
• Minimal and fast—~1KB gzipped, zero dependencies.
• Production ready—used in both Node.js and browser projects.

License

MIT

Powered by tahasoft-event-emitter – the robust TypeScript/JavaScript event emitter for modern apps.